1. Field of the Invention
This invention relates generally to motor protectors for protecting electric motors in sealed electric compressors against overload, and more particularly to a structure for mounting the motor protector, including a thermally responsive switch means making and breaking a power-supply circuit to the motor between a fixed contact and a movable contact secured to a bimetallic or other metallic thermally responsive member, which deforms in response to the changes of the temperature.
2. Description of the Prior Art
Conventional motor protectors for enclosed electric compressors are substantially thermally responsive switches. The thermally responsive switch is mounted outside or inside of a sealed housing in which an electric motor and a compressing means are provided. An overcurrent flowing into the motor or abnormal increase of the motor temperature is sensed by the thermally responsive switch, which opens contacts, to thereby interrupt the current flowing into the motor. The thermally responsive switch thus protects motor windings against overheat. The contacts of the thermally responsive switch are automatically reclosed afterwards to thereby allow the current to flow into the motor. If there is nothing wrong with the motor, the current is continuously fed to the motor. If there is anything wrong with the motor, making and breaking the power-supply circuit are alternately reiterated.
The motor protector of the type mentioned above has recently been mounted inside the sealed housing of the compressor rather than outside the sealed housing for improvement of motor protecting characteristics thereof. The motor protectors mounted inside the sealed compressor housing will hereinafter be referred to as "internal motor protectors" and those mounted outside the sealed compressor housing as "external motor protectors." Conventionally, the internal motor protector is embedded in a stator winding of the motor or placed close to the winding to be bound with strings, together with the stator winding. Since the sealed electric compressor has recently been rendered more and more compact, there is small space left within the sealed compressor housing in which the motor and the compressing means are provided. Consequently, it has become more and more difficult to ensure the space for mounting the motor protector on the stator winding. There has been a continuous need for solving the above-described problem, together with an economical solution for improvement of troublesome work in mounting the motor protector in the enclosed compressor.